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. 2022 Sep 29:9:1016961.
doi: 10.3389/fnut.2022.1016961. eCollection 2022.

Acetyl-glucomannan from Dendrobium officinale: Structural modification and immunomodulatory activities

Xiaoyu Guo  1 , Mingguan Yang  2 , Changlu Wang  1 , Shaoping Nie  3 , Steve W Cui  4 , Qingbin Guo  1
Affiliations

Acetyl-glucomannan from Dendrobium officinale: Structural modification and immunomodulatory activities

Xiaoyu Guo et al. Front Nutr. .

Abstract

To understand the mechanisms of immunomodulatory effect, Dendrobium Officinale polysaccharides (DOP) were treated by ultrasound and mild base separately to generate fractions of various weight-average molecular weight (Mw) and degrees of acetylation (DA). The structural features, conformational properties, functional properties and immunomodulatory activities of original and modified DOPs were investigated. Ultrasonic treatment decreased the Mw and apparent viscosity and improved the water solubility of DOP. Mild base treatment remarkably reduced the DA and the water solubility, while the overall apparent viscosity was increased. Conformational analysis by triple-detector high performance size-exclusion chromatography showed that the molecular chain of DOP turned more compact coil conformation with decreased DA. Results from the macrophages RAW 264.7 analysis showed that samples sonicated for 200 min (Mw 34.2 kDa) showed the highest immune-regulation effects. However, the immunomodulatory effects of the samples after de-acetylation were all compromised compared to the original DOP. This study inspires further research to establish the structural-immunomodulatory relationships, which promote the application of DOP in both the food and medicine fields.

Keywords: Dendrobium officinale polysaccharide; O-acetylation; glucomannan; immunomodulatory; structural modification.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
HPSEC elution profiles (A) and Infrared spectra (B) of the native and modified DOPs.
FIGURE 2
FIGURE 2
Logarithmic plot of the molecular weight vs intrinsic viscosity, radius of gyration of native and modified DOPs in aqueous solution. The Mark-Houwink plots of ultrasound (A) and de-acetylated (B) samples. The Rg power-law plots of ultrasonic (C) and de-acetylated (D) samples.
FIGURE 3
FIGURE 3
Polysaccharide induced proliferation and phagocytosis of macrophages. (A) Determination of optimal concentration (50, 100, 200, 400, 800 μg/ml). The proliferation and phagocytosis activities of ultrasonic (B) and de-acetylated (C) samples (100 μg/ml). All data are representative of at least three independent experiments. *p < 0.05 vs. control.
FIGURE 4
FIGURE 4
Polysaccharides induced production of immune factors NO (A,E), IL-6 (B,F), IL-10 (C,G), TNF-α (D,H) productions (24 h) by macrophages RAW264.7 exposed to ultrasonic and de-acetylated samples (100 μg/ml) were assessed by ELISA. All data are representative of at least triplicate culture.
FIGURE 5
FIGURE 5
Polysaccharides induced gene expression of cytokine IL-6 (A,D), IL-10 (B,E), TNF-α (C,F) productions (24 h) by macrophages RAW264.7 exposed to ultrasonic and de-acetylated samples (100 μg/ml) were assessed by RT-qPCR. Data are expressed as means plus SD of triplicate culture (different letters indicated significant differences at p < 0.05).
FIGURE 6
FIGURE 6
Schematic diagram of structural-conformational-immunomodulatory relationships of DOP The major structure of DOP adapted from Xing et al. (7).
See this image and copyright information in PMC

References

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